Empty loops.

compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/generators/BodyGenerator.kt

@@ -20,13 +20,14 @@ import org.jetbrains.kotlin.descriptors.CallableDescriptor
 import org.jetbrains.kotlin.ir.expressions.*
 import org.jetbrains.kotlin.psi.KtBlockExpression
 import org.jetbrains.kotlin.psi.KtExpression
+import org.jetbrains.kotlin.psi.KtLoopExpression
 import org.jetbrains.kotlin.psi.psiUtil.endOffset
 import org.jetbrains.kotlin.psi.psiUtil.startOffset
 import java.util.*
 
 class BodyGenerator(val scopeOwner: CallableDescriptor, override val context: GeneratorContext): GeneratorWithScope {
     override val scope = Scope(scopeOwner)
-    private val loopTable = HashMap<KtExpression, IrLoop>()
+    private val loopTable = HashMap<KtLoopExpression, IrLoop>()
 
     fun generateFunctionBody(ktBody: KtExpression): IrBody {
         resetInternalContext()
@@ -64,7 +65,7 @@ class BodyGenerator(val scopeOwner: CallableDescriptor, override val context: Ge
     private fun createStatementGenerator() =
             StatementGenerator(context, scopeOwner, this, scope)
 
-    fun putLoop(expression: KtExpression, irLoop: IrLoop) {
+    fun putLoop(expression: KtLoopExpression, irLoop: IrLoop) {
         loopTable[expression] = irLoop
     }
 

compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/generators/LoopExpressionGenerator.kt

@@ -44,7 +44,7 @@ class LoopExpressionGenerator(val statementGenerator: StatementGenerator) : Gene
     private fun generateConditionalLoop(ktLoop: KtWhileExpressionBase, irLoop: IrLoopBase): IrLoop {
         statementGenerator.bodyGenerator.putLoop(ktLoop, irLoop)
         irLoop.condition = statementGenerator.generateExpression(ktLoop.condition!!)
-        irLoop.body = statementGenerator.generateExpression(ktLoop.body!!)
+        irLoop.body = ktLoop.body?.let { statementGenerator.generateExpression(ktLoop.body!!) }
         irLoop.label = getLoopLabel(ktLoop)
         return irLoop
     }
@@ -105,7 +105,7 @@ class LoopExpressionGenerator(val statementGenerator: StatementGenerator) : Gene
         }
 
         val ktLoopRange = ktFor.loopRange!!
-        val ktForBody = ktFor.body!!
+        val ktForBody = ktFor.body
         val iteratorResolvedCall = getOrFail(BindingContext.LOOP_RANGE_ITERATOR_RESOLVED_CALL, ktLoopRange)
         val hasNextResolvedCall = getOrFail(BindingContext.LOOP_RANGE_HAS_NEXT_RESOLVED_CALL, ktLoopRange)
         val nextResolvedCall = getOrFail(BindingContext.LOOP_RANGE_NEXT_RESOLVED_CALL, ktLoopRange)
@@ -150,7 +150,9 @@ class LoopExpressionGenerator(val statementGenerator: StatementGenerator) : Gene
             statementGenerator.declareComponentVariablesInBlock(ktLoopDestructuringParameter, irInnerBody, VariableLValue(irLoopParameter))
         }
 
-        irInnerBody.addStatement(statementGenerator.generateExpression(ktForBody))
+        if (ktForBody != null) {
+            irInnerBody.addStatement(statementGenerator.generateExpression(ktForBody))
+        }
 
         return irForBlock
     }

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/expressions/IrLoop.kt

@@ -22,7 +22,7 @@ import org.jetbrains.kotlin.types.KotlinType
 
 interface IrLoop : IrExpression {
     val operator: IrOperator?
-    var body: IrExpression
+    var body: IrExpression?
     var condition: IrExpression
     val label: String?
 }
@@ -49,14 +49,12 @@ abstract class IrLoopBase(
             value.setTreeLocation(this, LOOP_CONDITION_SLOT)
         }
 
-    private var bodyImpl: IrExpression? = null
-    override var body: IrExpression
-        get() = bodyImpl!!
+    override var body: IrExpression? = null
         set(value) {
-            value.assertDetached()
-            bodyImpl?.detach()
-            bodyImpl = value
-            value.setTreeLocation(this, LOOP_BODY_SLOT)
+            value?.assertDetached()
+            field?.detach()
+            field = value
+            value?.setTreeLocation(this, LOOP_BODY_SLOT)
         }
 
     override fun getChild(slot: Int): IrElement? =
@@ -98,7 +96,7 @@ class IrWhileLoopImpl(
 
     override fun <D> acceptChildren(visitor: IrElementVisitor<Unit, D>, data: D) {
         condition.accept(visitor, data)
-        body.accept(visitor, data)
+        body?.accept(visitor, data)
     }
 }
 
@@ -125,7 +123,7 @@ class IrDoWhileLoopImpl(
     }
 
     override fun <D> acceptChildren(visitor: IrElementVisitor<Unit, D>, data: D) {
-        body.accept(visitor, data)
+        body?.accept(visitor, data)
         condition.accept(visitor, data)
     }
 }

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/DumpIrTree.kt

@@ -66,13 +66,13 @@ class DumpIrTreeVisitor(out: Appendable): IrElementVisitor<Unit, String> {
     override fun visitWhileLoop(loop: IrWhileLoop, data: String) {
         loop.dumpLabeledElementWith(data) {
             loop.condition.accept(this, "condition")
-            loop.body.accept(this, "body")
+            loop.body?.accept(this, "body")
         }
     }
 
     override fun visitDoWhileLoop(loop: IrDoWhileLoop, data: String) {
         loop.dumpLabeledElementWith(data) {
-            loop.body.accept(this, "body")
+            loop.body?.accept(this, "body")
             loop.condition.accept(this, "condition")
         }
     }

compiler/testData/ir/irText/for.kt

@@ -1,3 +1,7 @@
+fun testEmpty(ss: List<String>) {
+    for (s in ss);
+}
+
 fun testIterable(ss: List<String>) {
     for (s in ss) {
         println(s)

compiler/testData/ir/irText/for.txt

@@ -1,4 +1,17 @@
 FILE /for.kt
+  FUN public fun testEmpty(/*0*/ ss: kotlin.collections.List<kotlin.String>): kotlin.Unit
+    BLOCK_BODY
+      BLOCK type=kotlin.Unit operator=FOR_LOOP
+        VAR val tmp0_iterator: kotlin.collections.Iterator<kotlin.String>
+          CALL .iterator type=kotlin.collections.Iterator<kotlin.String> operator=FOR_LOOP_ITERATOR
+            $this: GET_VAR ss type=kotlin.collections.List<kotlin.String> operator=null
+        WHILE label=null operator=FOR_LOOP_INNER_WHILE
+          condition: CALL .hasNext type=kotlin.Boolean operator=FOR_LOOP_HAS_NEXT
+            $this: GET_VAR tmp0_iterator type=kotlin.collections.Iterator<kotlin.String> operator=null
+          body: BLOCK type=kotlin.Unit operator=FOR_LOOP_INNER_WHILE
+            VAR val s: kotlin.String
+              CALL .next type=kotlin.String operator=FOR_LOOP_NEXT
+                $this: GET_VAR tmp0_iterator type=kotlin.collections.Iterator<kotlin.String> operator=null
   FUN public fun testIterable(/*0*/ ss: kotlin.collections.List<kotlin.String>): kotlin.Unit
     BLOCK_BODY
       BLOCK type=kotlin.Unit operator=FOR_LOOP

compiler/testData/ir/irText/whileDoWhile.kt

@@ -1,7 +1,9 @@
 fun test() {
     var x = 0
+    while (x < 0);
     while (x < 5) x++
     while (x < 10) { x++ }
+    do while (x < 0)
     do x++ while (x < 15)
     do { x ++ } while (x < 20)
 }

compiler/testData/ir/irText/whileDoWhile.txt

@@ -3,6 +3,11 @@ FILE /whileDoWhile.kt
     BLOCK_BODY
       VAR var x: kotlin.Int
         CONST Int type=kotlin.Int value='0'
+      WHILE label=null operator=WHILE_LOOP
+        condition: CALL .LT0 type=kotlin.Boolean operator=LT
+          arg0: CALL .compareTo type=kotlin.Int operator=LT
+            $this: GET_VAR x type=kotlin.Int operator=null
+            other: CONST Int type=kotlin.Int value='0'
       WHILE label=null operator=WHILE_LOOP
         condition: CALL .LT0 type=kotlin.Boolean operator=LT
           arg0: CALL .compareTo type=kotlin.Int operator=LT
@@ -28,6 +33,11 @@ FILE /whileDoWhile.kt
               CALL .inc type=kotlin.Int operator=POSTFIX_INCR
                 $this: GET_VAR tmp1 type=kotlin.Int operator=null
             GET_VAR tmp1 type=kotlin.Int operator=null
+      DO_WHILE label=null operator=DO_WHILE_LOOP
+        condition: CALL .LT0 type=kotlin.Boolean operator=LT
+          arg0: CALL .compareTo type=kotlin.Int operator=LT
+            $this: GET_VAR x type=kotlin.Int operator=null
+            other: CONST Int type=kotlin.Int value='0'
       DO_WHILE label=null operator=DO_WHILE_LOOP
         body: BLOCK type=kotlin.Int operator=POSTFIX_INCR
           VAR val tmp2: kotlin.Int